For wiring substrates on which semiconductor chips or the like are mountable, there is a demand for fine-pitch electrodes to be connected to semiconductor chips or the like. For example, protruding electrodes formed mainly of tin (Sn) have been studied.
For example, a protruding electrode formed by forming a surface metal layer of a solder material on a conductive pillar protruding from an upper surface of an insulating layer by electroplating and thereafter melting the surface metal layer by a reflow process to cover the entire surface of the conductive pillar exposed on the upper surface of the insulating layer with the surface metal layer is proposed. (See, for example, Japanese Laid-open Patent Publication No. 2005-217388).